Vacuum casting equipment



Oct. 25, 1960 A. L. KRAFT VACUUM CASTING EQUIPMENT Filed Feb. 28, 1958 ./oww mw@ H Tw H AB H B P C R A l 9 M lun m w M 2 0 s JV 0 ./5 NL m o 5 2 m ma.. m mw A WT M. am 4 mmm n. .l l m mmf c m mwo\\ @i i U W..

|I| l l l l l l I llrllrllnlll D- l I I I I l I I III v N R N R Y V EMP 3 m.. Mm l- 3/ /m e wm u mm. Iii: 9 8 I; n l 7 R 4 l Il' .W n :I Il IL. V uw w 2 2 L m as me r I: 2 L m5 um 6 /9 w. .J ,Mm .nu III|II|I|I- -||l.-|| .L |IIW@ E C D llllllll lill-- R RH 2 U UK 0 0 s/ 3 s R mw .u 4 M .m m Ps W M T\ a P l F BACK PRESSURE 5W! TCH ATTORNEY 2,957,502 `Patented Oct. 25, 1960 VACUUM CASTING EQUIPMENT August L. Kraft, 120 Bender Ave., Roselle Park, NJ. Filed Feb. 28, 1958, Ser. No. 718,269

3 Claims. (Cl. 141-61) This invehtion relates to vacuum` casting devices, and more particularly to equipment of thisna'ture designed primarily for use` with dispensing apparatus which will automatically mix, meterv and dispense filled,rshort pot"- life epoxies, polyesters, polyurethanes and the` like. A major field of useifor the equipment is the encapsulation of electronic units.

Ase'rious" problem when' pouring molds is the elimination of: entrapped air bubbles. Such air bubbles tend to weaken the structurel of the molded pieces and may change the electrical and physical characteristics of encapsulated components. Various solutions to this problernVv have been suggested. Such solutions include; the redesignV of molds in an attempt to eliminate air" pockets, the` use of resinsV of lower viscosity and therefore of easier fiow, the use of reducedV flow rates, and attempts to lill the containers from the bottom up. The most widely used method consists of placing the filled molds in lchambersand then drawing a vacuum in an `attempt to pull the air bubbles out of the resin. These methods are expensive, time consuming and their resultsn are not uniforml-y satisfactory. v l,

In accordance with a major object of the present invention, a relatively inexpensive vacuum castingattachment may be afiixed to the face of the dispensing machine under the pouring spout. The structure includes an opening to permit the insertin of `the mold, which then rests upon a movable support. After sealing olf the opening, a vacuum pump exhausts air from the cavity* and molduntil `a predetermined vacuum level i'sattained. The mold is then moved into sealed relation with the pouring spout and catalyzed'resin is" poured into the mold under automatic control. ySince the resin and the catalyst may be degassed in their supply c'ont'airlers` and the material is poured into the vacuum chamber under positive pressure, no air will beadr'nitted into the chamberl from the dispensing' head. After filling, the cavity is opened' andthe air-free mold may then be removed. y,

An additional object of the'invention is the provision of equipment wh-ich will automatically pour the correct amount' of material into each can or mold regardless kof the' volumetric displacementA of the components in the cans, under conditions wherein the cans or molds are completely enclosed except for a small aperture through which they may be filledi Automatically pouring shots of fixed volume is-unsatisfactory inasmuch` as the total volumeof components to be encapsulated'will vary from one unit to the-next.

The system disclosed in my co'p'ending U.S. 'patent lapplication', Serial. No. 705,259, filed December 26, 1957. lends itself, with Very slight modification,` tothe attain*- ment of this objective when used with the structure which forms a part of the present invention. Since the container is in sealed relation to the dispensing nozzle, back pressure will be set up as soon as, but not until, the container is completely filled. This back pressure may then be utilized to put into operation suitable agencies to controly shut-'down ofthe system. The method may tion o-f the device is'as follows.

be accurately described by th'e term pressure-stalling.

A feature of the invention is a control system which makes possible a completely automatic cycle of operation. As a result, after operating a starting switch, the attendant is relieved of all duties other than the removal of filled molds when the cycle is completed, and the insertion of unfilled containers prior to the start of the next cycle.

in accordance with a further feature of the invention, a plurality of molds may be filled simultaneously.

These and other objects and features of the invention will be more fullyy apparent when considered in view of the detailed description which follows, reference being had to the accompanying drawings.

In the drawings:

iFig. 1 is a front elevation, with a diagrammatic showing of such connections to the pneumatic power system and to electrical circuits as are necessary to an understanding ofthe invention.

Fig. 2 is a circuit diagrarn showing the essential operating circuits of the device.

Referring now to Fig. l, a hollow chamber 1 whose `Valls are shown in section at 2, 2 is secured to the face plate of a dispensing machine. The invention is capable of use with a wide variety of mixing and dispensing equipments, but in the present instance, its operation will be described in combination with the system disclosed in the previously mentioned U.S. patent application Serial No. 705,259. Thus it will be assumed that the resin supply tube 10 is the supply tube 1t) of that application and that the spout 11 corresponds to the spout 11 of Fig. l of that application. The only other modification necessary to the disclosure ofv that application in order to adapt it for use with the present invention is the provision of a solenoid to operate the foot switch 91 shown in Fig. 3 of the application.

A bracket 3 secured to and extending out from the face plate has an aperture to receive spout 11 and serves as a support for guide rods 4 and 5. The bracket 3 also may function as the top closure for chamber 1.

fSpout 11 may terminate in a single nozzle, or if desired, may lead into a manifold 6, from which are extended multipley filling spouts such as 7. Bracket '3 also supports a microswitch 8 whose function willbe described hereinafter.

The lower ends of guide rods land 5 are secured to a bracket 9, which, like bracket 3', is secured to the face of the dispensing device in any convenient manner. A Second microswitch 12 is mounted-on bracket 9. Sleeves 13 and 14 are arranged for sliding motion on guides 5 and 4 and support la member 15 which is in fixed relation to the sleeves. Member 15 supports a sealing gasket shown in section at 16, 16. With member 15 in its uppermost position it, in combination with gasket 16, forms a sealing closure for the normally open bottom of chamber 1. A piston rod 17 is secured to a piston 18 which isin turn' slidable in cylinder 19. A lbearing 20 is secured to bracket 9 and serves as a guide for piston rod 17 which is slidable through both bracket 9 and member 15. A platform 21 is secured to piston rod 17 for motion therewith. Platform 21 serves as a 4support for the molds into which the casting material is to be' poured. Four molds have been shown at 22, 23, 24 and 25. A collar 26 is secured to piston rod 17 by means of a pin 27. Collar 2.6 supports a relatively stiff coiled spring 28 which Surrounds rod 17 and has a bearing against the under side of member 15. rlhe mechanical operation of this por- Upward motion of rod 17 imparts upward motion to platform 21. A corresponding upward motion is imparted to member 15 by Way of collar 26 and spring 28. Upward travel may continue until gasket 16 engages the lower edges of the walls of chamber 1. During this' operation the' pneumatic partly in section, together pressure applied to piston 18 is Asufficient to drive member 15 far enough to seal olf chamber 1 and operate microswitch 8. The pneumatic pressure is, however, insufficient to overcome the tension of spring 28 and the piston stalls in this position for the time being.

As will be more fully brought out hereinafter, automatic circuits are controlled by microswitch 8 to operate a solenoid controlled valve 29 which connects chamber 1 to a vacuum pump by Way of tube 30.

After a desired vacuum level has been attained, the control circuit, which will be described hereinafter, put-s into operation solenoid operated valve C, indicated at 31. During the upward motion of member 15, power was supplied to piston 18 upon the operation of solenoid operated valve A, indicated at 32. A pressure regulator 33 is employed and reduces the air pressure sufiiciently so that piston 18 is unable to overcome the tension of spring 28. However, upon operation of valve 31 full pressure is applied to piston 18. It then moves upward with sufficient power to overcome spring 28 and drive mold-supporting platform 21 upward until the molds engage the dispensing nozzles. In the upper portion of the drawing, dotted lines show the position of platform 21 and one of the molds just prior to the final motion of platform 21, but after the motion of the piston rod has been stalled. lt is evident that the molds must be so disposed on platform 21 that the filling apertures in the molds are in alignment with the pouring spouts with which they are respectively associated. Sealing gaskets 44 are preferably used to ensure that the mold and spout are in sealed engagement.

After the molds have been filled, the operation of back pressure switch 34 produces circuit changes which bring about the actuation of a solenoid operated valve E indicated at 35. Pneumatic pressure is thus introduced into cylinder 19 above piston 18 forcing it downward. Upon the completion of this downward motion, the return of member 15 to its normal position actuates microswitch 12 which then brings about the complete restoration of the system, and places it in condition for the start of a new cycle of operations.

lt is to be noted that the filled molds have been brought down to a position in which they may be conveniently removed by hand.

The operating circuits for the system will now be described. Referring to Fig. 2, a starting switch 36 is connected to conductor 37 extending to a source of power. A conductor 38 is connected to the other side of the power source. Momentary depression f switch 36 encrgizes a holding relay 39, the circuit of which returns to conductor 38 by way of the normally closed contact of pressure switch 34. Upon energization, relay 39 closes a locking circuit for itself by way of its normally open contact R. Relay 39 also opens its normally closed contacts R2, thus preventing energization of solenoid 35, the circuit of which is at this time also held open at the contacts of microswitch 12, inasmuch as member is in its normal position.

Simultaneously with the energization of relay 39, signal lamp 46 is lighted to indicate that a cycle of operation is in .progress and solenoid A is energized to apply reduced air pressure to cylinder 19. As has been previously described, upward motion of platform 21 and member 15 continues until microswitch 8 is operated. The closure of switch 8 completes a circuit for solenoid 29, which operates the valve which controls connection of exhaust line 30 to the vacuum pump. The application of suction to tube 30 actuates a vacuum operated switch 48, which in turn controls the energization of timer 41. Timer 41 may be of conventional structure and includes a traveling arm which will close a set of contacts after a preselected time interval. The time interval selected must be suflicient to permit the attainment of a satisfactory vacuum level within chamber 1. Upon the expiration of this time interval, normally open contacts 42 are closed by the timer and parallel circuits are completed for solenoids 31 and 43. Solenoid 31 operates valve C to increase the pneumatic pressure sufficiently to drive platform 21 upward until the molds are in sealed engagement with their respective pouring spouts. The energization of solenoid D operates switch 91 shown in Fig. 3 of application Ser. No. 705,259 and puts the dispensing equipment into operation.

The casting material is now delivered into the evacuated molds by way of the sealed connection between the spouts and the filling apertures of the molds. As a result, each mold may be completely filled without the introduction of air bubbles. Pouring continues until all molds have been completely filled. When this occurs, back pressure in supply tube 10 causes the operation of Switch 34. This switch is of conventional structure and is energized by motion produced in response to liquid pressure in a sylphon bellows or the like.

Switch 34, upon operation, opens its normally closed contacts and brings about the release of all previously energized equipment. The deenergization of solenoid 43 restores the operating switch of the dispenser, which is then prepared for re-operation. Lamp 46 is extinguished to notify an attendant that pouring has been completed. The release of relay R causes the closure of its normally closed contact R2, and inasmuch as the carriage is out of normal position, microswitch 12 is in closed position. As a result, the circuit of solenoid 35 is completed to cause the actuation of valve E which applies pneumatic pressure above piston 18 to drive the platform and sealing member down until normal position is reached, at which time the contacts of microswitch 12 are opened to release solenoid 35 and close valve E. It should be noted that during the return stroke of piston 1S the air below piston 18 may be displaced without back pressure by Way of a vent y45, which is open in the normal position of valve A with solenoid 32 deenergized. A solenoid operated valve having suitable operating characteristics for this purpose is Model V5D5550CT manufactured by the Skinner Electric Valve Division of the Skinner Chuck Company, New Britain, Connecticut.

Upon the release of solenoid 35, all parts of the apparatus have been restored to normal condition and the system is ready for reoperation.

It is obvious that casting chambers of a variety of shapes may be used, that the sealing means for the chamber may close an aperture in either the front or side of the chamber and that various forms of motion may be applied to the movable support for the molds without departing from the spirit of my invention.

What is claimed is:

1. A vacuum casting device including in combination, casting material, automatic dispensing apparatus, a dispensing spout associated therewith, means to dispense said casting material from said spout under positive pressure, a hollow chamber encompassing said spout, a mold, an opening therein, a movable support within said chamber to receive said mold, sealing means for said chamber, means to exhaust air from said chamber and from said mold until a predetermined vacuum level has been attained, means operative thereupon to move said support until the opening in said mold is in sealed engagement with said spout, means including said dispensing apparatus to pour casting material into said mold from said spout, and automatic means effective in response to the back pressure created when the mold and its associated spout have been completely filled to disable said dispensing apparatus.

2. A vacuum casting device including in combination, casting material, automatic dispensing apparatus, a dispensing manifold associated therewith, a plurality of dispensing spouts supplied by way of said manifold, means to dispense said casting material from said spouts under positive pressure, a hollow chamber encompassing said spouts, a plurality of molds, a lilling aperture in each of said molds, a support within said chamber to receive said molds, means to exhaust air from said chamber and said molds until a predetermined vacuum level has -been attained, means operative thereupon to move said support until the lilling aperture in each of said molds is in sealed engagement with an individually associated one of said spouts, means including said automatic dispensing apparatus to pour casting material into said molds, and means -automatically elfective in response to the back pressure created when all of the molds and Vtheir associated spouts have been completely filled to disable said dispensing apparatus,

3. A vacuum casting device including in combination, casting material, automatic dispensing apparatus, a hollow chamber encompassing a dispensing spout, a mold, a filling aperture therein, sealing means for said chamber, pneumatic actuating means to provide motion for said sealing means, a movable platform to support said mold, a starting switch, electrical circuits controlled thereby, a source of air-pressure, regulating means therefor, means including said electrical circuits to apply regnamed switching device to apply unregulated air-pressure to produce motion of said support to bring the iilling aperture of said mold into sealed engagement with said pouring spout.

References Cited in the iile of this patent UNITED STATES PATENTS 314,352 Stevenson Mar. 24, 1885 1,909,575 E11 et al. May 16, 1933 2,329,426 Valiton Sept. 14, 1943 2,428,598 Weaver Oct. 7, 1947 2,661,885 McBean Dec. 8, 1953 2,745,585 Lindars May 15, 1956 2,839,093 McCarthy June 17, 1958 

